This section introduces aspects that may facilitate a better understanding of the disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
Mobile broadband continues to drive a demand for higher overall traffic capacity and a higher achievable end-user data rate in a radio access network. Several application scenarios in the future will require data rates up to 10 Gbps in local areas. The demand for very high system capacity and very high end-user date rates may be met by networks where a distance between access nodes ranges from a few meters in indoor deployments up to roughly 50 m in outdoor deployments, i.e. with an infra-structure density considerably higher than the densest networks of today. The wide transmission bandwidth required for providing a data rate up to 10 Gbps and above may only be obtained from spectrum allocations in the millimeter-wave band. High-gain beamforming, typically realized with array antennas, may be used to mitigate the increased path loss at higher frequencies.
MMW networks have a number of properties that, generally speaking, make operations under the shared spectrum promising. Due to a small antenna size at high frequencies, MMW networks heavily rely on high-gain beamforming, which enables significantly higher resource reuse and alleviate interference between multiple networks. It is expected that these networks will predominantly be deployed in the form of “high-capacity coverage islands” in areas where a very high traffic demand is expected or a very high connection speed is required, which means that an area will normally be covered by one network only rather than having multiple parallel networks deployed by different operators. Hence, inter-network interference may predominantly occur between partially overlapping, adjacent or neighboring, i.e. with a certain distance in-between, networks. In such a situation, it is preferable to avoid fragmentation of the available bandwidth into one exclusive sub-band per network, since a large amount of spectrum would remain unused at times when networks are not simultaneously fully loaded, and peak data rates would be limited to a fraction of what could theoretically be achieved. It would instead be preferable that each MMW network may access the full available frequency bandwidth so order to maximize spectrum utilization and support peak data rates. In this case, inter-network interference may be unavoidable.
FIG. 1 illustrates an inter-network interference situation between two operating networks sharing a spectrum, which may be two MMW networks, wherein a first operating network shown with a dotted pattern comprises three access nodes AN1-AN3 which serve user equipment UE1-UE3, respectively and a second operating network shown with a striped pattern also comprises three access nodes AN4-AN6 which serve UE4-UE6. The two operating networks are located in a same area and operate on a same channel. Hence they may cause interference to each other. The interference between links in different networks may be bidirectional or uni-directional. For example, link A1 between AN1 and UE1 in the first operating network may cause interference to link B1 between AN4 and UE5 in the second operating network, which is illustrated with a single head arrow; and link A2 between AN2 and UE2 in the first operating network may cause interference to link B2 between AN6 and UE6 in the second operating network and vice versa, which is illustrated with a double head arrow.
In this case, it would be necessary to find a technology so that residual interference in border areas between two independent networks may be handled in an efficient way, which is called interference coordination.
In order to support the above spectrum sharing scenario as illustrated in FIG. 1, several existing solutions have been proposed.
Wireless Local Area Network LAN systems, like IEEE 802.11 systems support such a scenario based on contention-based access to radio resources. However, the principle of the contention-based access has a fundamental issue that overhead grows proportionally when the system load increases. In combination with beamforming, this issue would be even more significant due to existence of hidden node problems.
Coordinated intra-network or inter-cell spectrum re-use is already widely studied in current cellular networks. For example, the Almost Blank Subframe (ABS) concept has been intensively studied to reduce interference between third generation partnership project long term 3GPP LTE Macro and Pico cells in heterogeneous network scenarios. Similarly, the Dynamic Point Blanking (DPB) concept has been proposed to improve performance of Coordinated Multi-Point (CoMP) transmission and reception. However, resource coordination for inter-network spectrum sharing networks differs from intra-network coordination in a number of aspects as below.
Firstly, inter-network interference may be stronger than intra-network interference since a mobile terminal belonging to a network may be closer to a transmitter in another network to which the mobile terminal is not permitted to connect. Therefore, the potential benefit of inter-network resource coordination is more significant.
Secondly, coordination objectives are different. The objective of the inter-network coordination is mainly focused on fairness and equitable access to spectrum resources. Whereas, the objective of the intra-network coordination is to improve overall network capacity, which means it is acceptable that one of the coordinating entities sacrifice itself for the benefit of overall sum utility.
Thirdly, the inter-network coordination shall be slower than the intra-network coordination in time scale, so as to obtain a basis for network internal radio resource management that may be valid for relatively long time.
Therefore, the existing intra-network interference coordination technique may not applicable to the inter-network resource coordination.
Other existing link-specific coordination context-based solutions as proposed in PCT applications PCT/CN2014/070999 and PCT/CN2014/070997 may achieve the inter-network resource coordination between different MMW networks sharing a spectrum. However, the link-by-link coordination may result in more overhead since for each coordinated link, a certain amount of information have to be exchanged between the involved networks. If such information is transmitted over-the-air, it will reduce or even level out performance gains from the interference coordination; and in an extreme case, it may even lead to lower performance compared to an uncoordinated baseline case.
Hence, there is a need for a solution to coordinate scheduling of interfering links between different MMW networks so that interfering transmissions do not or at least less probably end up on the same radio resources, while reducing the amount of information exchanged between the networks.